actually,I want creat a MCAT for another system,and I got a volumn with system datasets SYS1.*, then I attached this volumn to my testing environment,created a UCAT,then I want a faster way to catalog this dataset to my UCAT.

[quote="enrico-sorichetti"][quote]are You trying to clone an existing system ???quote]

I'm trying to creat a mini system,I copied system datasets to a volumn from a online working system, then I attach this volumn to another testing environment,fisrt step I created UCAT,and I need catalog all dataset on this volumn to my UCAT

If you repro mergecat from catalog1 to catalog2. Catalog2 is now the owner of the datasets. Entries are deleted from CATALOG1. Repro mergecat is used for moving or splitting catalogs not for copying catalogs